PATENT REPORT - INTERIM

• Document Type: CREST
• Collection: NGA Records (Formerly NIMA)
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78B04770A002800040027-0
• Release Decision: RIPPUB
• Original Classification: C
• Document Page Count: 39
• Document Creation Date: December 28, 2016
• Document Release Date: May 24, 2005
• Sequence Number: 27
• Publication Date: August 30, 1966
• Content Type: LETTER

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Post Office Box 8043
Southwest Station
Washington, D. C. 20024
164-54-4
Copy of 4
25X1
5X1
114
- -- 4s pin I. #Ys/ F.L.L .Leas.
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Subject: PATENT REPORT - INTERIM
Reference: Contract
Task Order o. 02
Gentlemen:
The work under docket
covrs an invents de during 25X1
DOCKET INVENTOR TITLE
f
in
o mat ion Recording by Bleaching
Dye Azide Composition
Since this invention was in the early stage of its development at
the time it was docketed, it has not been decided whether a
patent application should be filed. If the inventor's opinion
of the work is supported by results of additional work, a patent
application will be filed. You will be advised of our decision on
this point as soon as the work reaches a point where a sound patent
decision can be made.
A copy of the patent docket letter is attached.
EXCLUD D r uM AUTOMATi C
GIWN1~1q )D NJ
Distribution:
Copies 1 and 2 - Contracting Officer
.:,y 3 - Technical Representative
Copy 4 - File
Declass Review by GROUP I
N GA.
25X1
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Contract No._J
Task. No. 02
Progress Report No. 12
Covering the period Au et 1 - September 16, 1966
Financial Status
Amount Authorized . . . . . . . . . . . . . .
Estimated-.-Expenditures thru 9/11/66
Funds. Committed . . . . . . . . . . . . . . .
Funds Remaining . . . . . . . . . . . . . ...
Technical Status
Attached is a technical progress report covering
the period of l August to 16 September 1966. Enclosures
referred to in report are attached to original only.
i5a
.-Distribution:
Technical`.Representative - three copies
Contracting Officer - tWO Copies
.File OnO COPY
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Progr. ess l"efort //12
Photobleach Photography Phase II
August 1 - September 16, 1966
Screening _Experiments
The effort during August consisted of a continuation of previous work, i. e. ,
screening of dyes and of mixtures. Several yellow dyes were tested, as were
several mixture modifications without achieving any striking results.
DEMI and TMI
At the end of August, two new dyes were received and tested. These dyes,
N, N-diethyl-2-methylindoaniline and N, N, 2-trimethylindoaniline, code names
DEMI and TMI respectively, had been synthesized for this program. The
work on these dyes will be the main topic of this report.
DEMI and TMI are blue dyes of similar structure, and related to Indophenol
Blue, which has been extensively studied in this program. Films of DEMI or
TMI sensitized by iodoform or carbon tetrabromide when exposed for 0. 5 to
10 seconds (depending on light source, concentration of materials in film, and
similar experimental factors) will show little or no evidence of bleaching.
After heating for a few minutes, however, in an oven at about 100?C, the
exposed areas will bleach resulting in a positive reproduction of the transparency
used. The interesting aspect of this is that the contrast of the reproduction
depends directly on 'the time of heating. That is, short heating times lead to
images of low contrast, and as heating time is increased, the areas with greatest
exposure decrease in density thus increasing contrast.
If use is to be made of this method of contrast control, the films cannot be heat
fixed in the usual way, since heat fixing involves a longer heating period than
that needed to develop the image. Several methods of solving this problem are
possible. The simplest is to take advantage of the insensitivity of the films to
-light of wavelength greater than about 5000 A. Films protected by Wratten #15
filters, for example, can be exposed to intense light without damage. Such
protected films have been exposed for ten minutes in a 500 watt projector
without observable change. When viewed on a light table, the image in these
protected films appears black or blackish green on a yellow background.
If heat locking is to be used, it is possible that contrast control can be achieved
by careful control of exposure, once optimum heat locking conditions are
determined. Heat locking for these materials is difficult, although it has been
accomplished. In most cases in which it has been tried, the films have been
over-exposed and have been almost completely bleached during heating. The
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achievement of reproducible heat locking will require a program of extensive
empirical testing of both exposure and heating conditions, utilizing reproducible
films.
Conceivable fixing methods which avoid the problems of both the above
a]t.c,rnatives anni~acle (1) a solvent wash by some solvent that will, dissolve
iodoform but not the dye or polymer, or (2) prolonged exposure to high vacuum
without heating which presumably will remove the iodoform by evaporation.
We have no direct experience with either of these methods.
Work with the above dyes has been done both on glass and on Mylar tape. Some
time has been devoted in the last week to acquisition of some rudimentary tape
coating technique. Some examples of tape, all of which were given the same
exposure but different heating times, are enclosed with this report, together
with the negative used in the exposure. Since the films are not heat locked,
they should not be exposed to intense light without the protection of a yellow
filter. A Wratten #15 filter is also enclosed. .
Photometallic Process
A quite different technique for producing direct positives based on the "Photo-
metallic Process" being studied in this laboratory has recently been proposed.
In this process, a metal film (gold, silver, tin, and other metals have been
used) is overlaid with a photoreactive material in a polymeric binder. On
exposure to light, the metal surface is etched. The polymer film is then washed
away. The remaining metal film is a direct positive reproduction of the mask
used in the exposure. An example of a silver film on glass is enclosed with
this report. Exposure was 45 seconds, to a 500 watt projector. It will be seen
that the image looks metallic by reflected light, but looks blue black by
transmitted light, as in a projector. The blue color is characteristic of light
transmitted through thin films of silver. Other metals, particularly tin, do not
have such windows in the visible region. The process is equally applicable on
Mylar tape as on glass.
Plans for September-October
Work will be continued on the DEMI and TMI systems, and on films on tape.
If desired by the sponsor, work on the Photometallic Process will be started.
The next report will be for the period Septerrber 19-October 21. The time
remaining after October 21 will be devoted mainly to the final report.
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25X1 Contract No.
Task No. 02
Progress Report No. 11
Covering the period ly 95 6
Fi4ancial Status
Amount Authorized . . . . . . . . . . . .
25X1
Funds Committed . . . . . . . . . . . . .
Funds Remaining . . . . . . . . . . . . .
Estimated-_Expenditures thru 7/31/66
Technical Status
Attached is a technical progress report covering
the period of July l86.
J.
Technjcal`Representative - three copies
Contracting Officer - two copies
-File - one copy
25X1
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Progress Report #11
Photobleach Photography Phase II
July 1966
The effort during July was concentrated on the screening and evaluation
of new dyes and mixtures, and on broadening understanding of previously
used materials. Fourteen green dyes were obtained and tested. These
showed low sensitivity but a few bleached to yellow. Four yellow dyes
were tested with negative results. It was noted that a small amount of a
green dye in a Rose Bengal film deepens the over-all color markedly,
and results on a very fast film with good contrast between bleached (pale
green) and unbleached (dark purple) areas.
Experiments have been run on several mixtures to determine heat locking
conditions more precisely. It was found that high temperature (above
120?C) heat locking is not feasible for certain dye-PSA combinations,
particularly Rose Bengal-CBr4, due to thermal reactions, while several
other combinations heat lock very nicely at high temperatures.
Plans for August. Screening of dyes is to be continued. Black mixtures
are to be prepared for demonstration purposes. Some work will be done
on systems which do not require heat locking. A 400 watt mercury lamp
is to be put into operation, which will facilitate work with films needing
near ultraviolet exposure.
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Contract No.
Task No.
Progress Report No.
Covering the period
Juno IOC'
Financial-Status
Amount Authorized . . . . . . . . . . . . . .
.Estimated--Expenditures thru 7/3/66 . . . .
-Funds .Committed . . . . . . . . . . . . . . .
Funds Remaining . . . . . . . . . . . . ...
.Technical Status
Attached is a technical progress
the period o June 19"C3
my ItK~Li
.-Distribution:
Technical' Representative - three copies
Contracting Officer - two co1ief
.File .. one copy
report covering
25X1
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Progress Report #10
Photobleach Photography Phase 11
The screening of blue and of green dy,~:- has continued. In addition, some of the
dyes were incorporated into black mixtures and evaluated. None of the dyes or
mixtures showed outstanding properties. Several new dyes having appropriate
color changes in acid have been ordc red, and will be evaluated in July.
A brief experiment to determine the (,ffect of heating during exposure on the
H&D curve was performed. H&D curves (optical density plotted against log
exposure) were plotted for two samples of a Rose Bengal-iodoform film. During
one exposure the film was held at roorr, temperature, while during the other the
temperature was raised by a stream of warm air. The respective slopes of the
H&D curves were 1. 6 and 2. 0. We have thus demonstrated that the slope of the
H&D curve can be increased by heating during exposure. The question of whether
such heating will affect photographic contrast during normal photographic exposure
still remains to be answered, however.
We wish to request an extension in time for completion of the present contract,
at no additional expense to the sponsor. The delay in the project has been caused
by a manpower shortage which we have not been able to remedy. One of the two
technicians employed on the project took a leave of absence during April and May
in order to complete the requirements for his Bachelor's degree. Instead of
returning to the project in June, as scheduled, he accepted a professional
position elsewhere. We have not been able to find a satisfactory replacement for
him as yet. At the present level of activity, we estimate that the project will be
completed by November 10, although an earlier date is possible should appropriate
personnel be found. The additional time requested will make it possible for us to
complete more satisfactorily the requirements of the present program with the
personnel now available.
Plans for July. The screening of dyes and evaluation of mixtures will be continued.
Quantitative work on the effect of temperature on exposure parameters will be
commenced.
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Contract No.
Task No. 02
Progress ReportNo.
Covering the period May 1966
Financial Status
Amount Authorized . . . . . . . . . . . . . .
Est imated-_ Expenditures thru 5/29/66 . . . .
Funds. Committed . . . . . . . . . . . . . . .
.Funds Remaining . . . . . . . . . . . . . ...
Technical Status
Attached is a technical progress report covering
the period of May 1966.
-Distribution:
Teehnical'.Representative - threo copies
Contracting Officer - two copies
.File - one copy
25X1
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Progress Report #9
Photobleach Photography Phase II
May 1966
Evaluation of mixtures continued as the major effort in May. Formulations
based on Pinacyanol and Rose Bengal appeared very promising, showing
good color and sensitivity properties. It was eventually determined, however,
that Pinacyanol could not be completely fixed, as it has an inherent light
sensitivity. As a result, Pinacyanol films which had been heat locked after
exposure faded perceptibly when left in room light for a day or two. Work on
Pinacyanol has therefore been terminated, and the search for a good blue dye
reinstituted.
An apparatus has been built to investigate the variation of sensitivity of dye
films with temperature. An approach to the control of contrast based on the
temperature-sensitivity relationship has been formulated, and presented in
the proposal for Phase III of this project. Although the major effort on this
problem will be made during the next contract year, a brief attempt to
demonstrate the feasibility of the approach will be made in late June or July,
when the apparatus will be in operation.
Some photosensitive agents, which had not been previously tried, were tested
briefly. Pentabromoethane proved to be slower than carbon tetrabromide,
and hexachloroethane required ultraviolet exposure. Films were made up of
various dyes in Saran (polyvinylidenechloride) and in polyvinylchloride
(PVC), with the polymer serving as photosensitive agent. These films
bleached with ultraviolet light, with the Saran films more sensitive than the
PVC films. Some dyes proved stable to visible light in these r films, while
others bleached in white light. The behavior of the dyes in these media, with
respect to wavelength sensitivity, was similar to that observed previously
with added photosensitive agents such as iodoform.
Plans for June. Screening of dyes will be continued with emphasis on blue
dyes having good color and sensitivity. Evaluation of mixtures will be
continued. Further work on flexible substrates and on Saran films will be
done, and the temperature studies will be initiated.
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Task No.
Progress Report No.
-Covering the period
Financial-Status
Amount Authorized . . . . . . . . . . . . . .
.Estimated--Expenditures thru 4/30/66 . . . .
Funds Committed . . . . . . . . . . . . . . .
,Funds Remaining . . . . . . . . . . . . . ...
Technical Status
Attached is a technical progress report covering
the period of Aorll 19".
June 1900
-Distribution:
Techni.cal'.Representative - tree copies
Contracting Officer - two copies
File one copy
25X1
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Progress Report #8
Photobleach Photography Phase II
April 1966
The major effort during April was in the screening of dye-photosensitive
agent combinations. A large number of such systems were prepared and
run. Pinacyanol, a blue dye with good properties, was processed at the
end of the month. Pinacyanol gives a deep blue, with high optical density
available in the wavelength range of 540 to 650 nm. Bleaching properties
are good, with an almost colorless product obtained in some examples.
Sensitivity is moderately high.
A second field of activity was in the use of vacuum during heat locking.
Several experiments were performed to see if vacuum would increase the speed
of heat locking. Contradictory results were obtained. Further work on
this is necessary.
During the heat locking experiments, it was found that exposure of the slides
while warm would increase the photographic speed markedly. The potential
value of this observation lies in that it gives us the ability to vary the
sensitivity of a given material, and probably the gamma, although this is by
no means certain as yet.
Plans for May
Mixtures of dyes based on Pinacyanol and Rose Bengal will be investigated.
Vacuum heat locking measurements will be continued. Apparatus will be
designed and constructed for constant temperature exposures so as to measure
the variation of sensitivity with temperature quantitatively, and to determine
whether or not temperature variation is a feasible means for gamma control.
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25X1
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Contract No.
Task No. 02
Progress Report No. 7
Covering the period March 1066
Financial Status
Amount Authorized . . . . . . . . . . . . . .
Estimated -Expenditures thru 4/3/66 . . . .
Funds Committed . . . . . . . . . . . . . . .
Funds Remaining . . . . . . . . . . . . . . .
Technical Status
Attached is a technical progress report overing
the period of March 1966.
Distribution:
Technical Representative - three copies
Contracting Officer - two copies
File - one copy
25X1
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Progress Report #7
Photobleach Photography Phase II
Several additional blue and black dyes have been screened during March, and
again there has been no discovery of a dye with outstanding properties.
Similarly, screening of polymers and solvent systems is continuing. As an
example of the polymer work, a polysulfone resin was investigated. The film
formed from this polymer had the interesting property of being readily peeled
off the glass support on which it was cast, resulting in a flexible, cohesive
film with moderately good optical properties.
A series of runs was made on the effect of concentration of Rose Bengal and
iodoform on quantum efficiency. The ratio of Rose Bengal and iodoform was
kept constant, but the concentration of the reactants on the polymer film was
varied. The light used was absorbed by the Rose Bengal only. The quantum
efficiency proved to, be relatively independent of initial concentration except
at very low initial concentration, equivalent to optical density of 0. 7. or less.
For low concentrations, quantum efficiency was lower than at higher
concentrations.
A small vacuum oven was obtained for further heat locking experiments. The
experiments which had been reported previously were performed in a glass
apparatus that was inconvenient to manipulate and to regulate. Preliminary
results indicate that the new equipment may prove quite useful in these
experiments.
Plans for April
Screening of dyes and polymers is to be continued. Tests on heat locking
under vacuum will also be continued. Further effort in synthesis of a blue
derivative of Rose Bengal will be made. .
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Contract No.
Task No. 02
Progress Report No. 6
Covering the period February 1966
Estimated Expenditures thru 2/27/66 . . . .
Funds Committed . . . . . . . . . . . . . . .
Funds Remaining . . . . . . . . . . . . ...
Technical Status
Attached is a technical progress report covering
the period of February 1966.
Distribution:
technical Representative - three copies
Contracting Officer - two copies
.File - one copy
25X1
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Progress Report #6
Photobleach Photography Phase II
lrebruary 19613
Several blue and black dyes have been screened for photoreactivity using
white light and also ultraviolet. Results so far have been disappointing in
that none of the dyes examined has shown any improvement in properties
over those already in use, such as Indophenol Blue. This screening is
being continued. In addition, screening of polymer and solvent systems
is continuing, both to provide further compatibility capability, and in the
hope of finding polymers that will act as sensitizers. Among the dyes
investigated were some interesting cyanine dyes with good color and
reactivity properties, but which were not sufficiently soluble in any of the
polymers we have yet used to make a dark film. Hence the need for
greater compatibility.
A comparison has been made of the quantum efficiency of the photoreaction
of Rose Bengal with iodoform and with CBr4. The measured quantum
efficiencies were essentially equal, when light absorbed by the dye alone
is used. This result is significant in that the transfer of energy from the
dye to the photosensitive agent does not seem to depend on the bond strength
of the photosensitive agent.
An experiment was performed to see if loss of speed of the films on storage
is due to loss of residual solvent. Several identical films were made up,
and some were sealed into polyethylene bags. Rates of bleaching of the
fresh film, of film stored in the bags for a month, and films stored in the.
customary box for a month were compared. The results indicate that
storage of these particular films in polyethylene results in about 25% less
loss in sensitivity. Other types of packaging and other types of films will
be investigated in the future.
Plans for March
Screening of dyes and polymers is, to be continued. In addition, a series
of runs is planned to determine the effect of local concentration (at constant'
ratio of reactants) on sensitivity. Preparation of derivatives of Rose
Bengal which are expected to be blue will also be commenced.
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III. INTRODUCTION: OBJECTIVES AND PRESENT STATUS
Photobleach Photography is a process in which a dye or mixture of
dyes, in combination with a photosensitive agent, bleach or change color
upon exposure to light. The process is dry, non-reversible and results in
continuous tone, high resolution images. Since the dyes are bleached by
light, positive images of positive transparencies are obtained. Heating
fixes the film so that it is no longer sensitive to light.
The objectives originally proposed for this process were those to
have been achieved ultimately in a long range program of research and
development. More recently, a more limited set of objectives have been
specified. The modifications have been based on the properties immediately
desirable in a practical, useful film, and on the experience derived during
the course of the program.
The short term. objectives to be attained are as follows:
1. Black and white (or colorless) film, with Dmax = 2. 0 or more,
over the visible region, and Dmin = 0. 1 or less.
2. Resolution capability of 200 lines/mm.
3. Response latitude of at least eleven steps of a standard step
wedge.
4. Sensitivity such that a 4 x 5 copy can be made in 30 seconds
or less, using a total power of 1100 watts for exposure and all associated
equipment.
$. Ability to control the photographic characteristic curve and
thereby vary gamma from 1. Q to 2. 0.
S. Ability to utilize a variety of substrates for the photosensitive
film, e. g. Mass, flexible transparent tape with stability comparable to
Mylar, and paper,
7. :Fixing time of one minute or less.
B. Storage stability for a period of a year before exposure and
six months after exposure.
9. Short time stability to room lights before exposure and/or
fixing to eliminate dark room procedures.
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Each of these objectives, except for the color characteristics and
the control of contrast, has been achieved separately but not simultaneously.
For example, rapid (one minute) heat fixing has not yet been accomplished
without serious deterioration of resolution. The major objective of the
present proposal is to achieve all of the nine objectives above simultaneously
in the same material. As it is expected that the desired color
characteristics will be achieved during the current program, the objectives
of the present proposal are:
1. to develop a technique for the control of contrast, and
2. to develop methods for combining all the desired properties
into one photosensitive medium.
A brief review of the present status of the current program will
serve as an introduction to the detailed technical proposal.
A. Optical Density and Color. The attainment of the desired
optical density range depends on the choice of a group of dyes, each of
which will provide the desired Dmax over some portion of the visible
spectrum, and will individually provide a Dmin somewhat less than the
desired value over the entire visible spectrum. In addition, an appropriate
combination of dyes of the group should give the physiological sensation of
black. Films of individual dyes have been made which meet the above
requirements, but combinations which meet all the requirements are not
yet available. The best combination film thus far had a Dmax averaging
2. 5 through the visible spectrum, and Dmin of about 0. 3-0. 4 in the region
from 5000 A? - 7000 A?. At wavelengths below 5000 A?, Dmin was
considerably higher, resulting in a tan appearance.
Progress is being made in this aspect of the work. New
combinations of dye and photosensitive agent are continuously being tested.
It is expected that, at the present rate of progress, the requisite-Dmax
and Dmin over the visible spectrum will be available by the end of this
program.
B. Resolution and Fixing. Theoretically, the ultimate resolution
capability of the material is limited by the wavelength of light (about
1000 line pairs/mm in the visible region). In practice, the resolution may
be affected by diffusion, particularly during the heat fixing step, and by
mechanical vibration during exposure. A resolution of 350 line pairs/mm
was demonstrated in a crude experiment very early in the program.
However, pronounced loss of resolution has been observed in some samples
after prolonged high temperature fixing.
-4-
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Heating fixes the films by volatilizing the photosensitive
agent. Practical fixing conditions depend on a combination of factors.
For a given film, fixing time decreases by a factor of about two for every
ten degree rise in temperature, To ac#iieve a fixing time of one minute,
a temperature of about 160PC is needed. At this temperature, resolution
is severely degraded in our Materials, and Mylar is badly distorted.
Heat fixing has been done almost entirely in a conventional
laboratory oven. Several experiments have been performed in a vacuum
oven, and others with an infrared lamp. Other techniques such as forced
hot air will also be tried. The evidence so far is not conclusive but seems
to indicate that considerable modification of the presently used films and
techniques will be needed for short time heat fixing to be effective. One
such modification is based on the observation that heated films exhibit
much greater sensitivity than films at room temperature. If a heated film
is used to provide increased sensitivity, a smaller amount of photosensitive
agent can be used, and thus reduce fixing time. This solution to the
problem is undesirable, however, since the temperature control of the film
will be necessary for other purposes to be discussed later.
C. Latitude. A response latitude of fourteen steps has been
demonstrated on representative materials. There seems to be no reason
to believe that the latitude response will be seriously affected by the
nature of the materials used, as long as similar colors are employed. The
more nearly the material meets the color specifications, the greater the
latitude it will show, because of the eye response, and because of the
density range available.
D. Sensitivity. The sensitivity requirements in the list of
objectives is stated as an operational requirement because the terminology
developed for silver halide materials is not readily applied to photobleaching
materials. It is more appropriate to define the task to be accomplished,
than to specify arbitrary numbers for sensitivity, which might prove either
insufficiently high to accomplish the task, or unnecessarily high for that
task.
For comparison of dyes, formulas have been developed which
give.a number for the sensitivity which is related to that of silver halide
materials under specific conditions. The formulas have the form
S = 0. 147a
a
taw (100-Tav)
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where Sa is the sensitivity value based on a change in optical density of
a units from the initial optical density,
change of a,
ta is the time, in secondq to achieve an optical density
r^
L
w is the energy falling on the film in mw/cm2,
and therefore taw is the exposure in mw-sec/cm2,
and T is average percent transmission of the film
during the exposure. av
The exposure needed to achieve a darkening of 0. 1 optical
density unit in a reference silver halide film, ASA = 1. 0, gamma = 1. 0
is used as a parameter in the above formula. Sa, the sensitivity, is the
ratio of that exposure of the silver halide film to the exposure needed to
effect a bleaching of 0. 1 density unit of the photobleach film under
investigation. In that sense, Sa is a direct comparison of photobleach
material sensitivity with the standards set for silver halide materials.
Several individual dyes which meet the operational sensitivity requirement
have been derived. Some are an order of magnitude more sensitive than
the minimum specified. The sensitivity values for these materials are
about 2 x 10-6 to 3 x 10-5.
E. Contrast Control. No experimental work has yet been done
on this problem. An approach to the achievement of contrast control is
discussed in Section IV, B, and constitutes a major portion of this proposal.
F. Substrates. Most of the photosensitive films have been cast
on glass. Some of these films can be stripped from the glass backing and
used as flexible films. Other films have been cast on Mylar or other
flexible substrates, and on paper. Dye-photosensitive agent combinations
have been absorbed by paper, and also by Mylar. Although the properties
of the materials absorbed by paper are rather different from those of the
polymer films cast on transparent substrates, there do not seem to be any
fundamental limitations to the use of all of these substrates.
G. Material Storage. The present materials exhibit a sensitivity
decrease in the first few days after preparation. The sensitivity
subsequently remains relatively constant or decreases very slowly for
long periods of time. The sensitivity loss is estimated to be a factor of
about 2 to 2. 5 over a year. Packaging of the materials reduces the loss
of sensitivity, and may eventually eliminate it. Further, the sensitivity
loss can be eliminated by warming the materials. Although not yet
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investigated quantitatively, it is believed that the sensitivity loss is due to
loss of residual solvent, or to slow air oxidation.
Exposed materials can be stored indefinitely in the dark without
fixing. After fixing, some materials can be exposed for long periods to
bright light sources. Others have proven inherently light sensitive and can
only be exposed to moderate intensities, as on a light table, for periods of
a few hours. Dyes in this last category will not be used in the final film.
H. Handling in Room Light. Very few of the formulations
prepared to date are sufficiently sensitive so that handling for several
minutes in normal room light produces noticable degradation of density...
Exposure for long periods (hours), however, produces bleaching.
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IV. TECHNICAL PROGRAM, PHASE III, 1966-1967
The primary goal of the Phase III program will be to develop'..a,
film meeting all of the objectives listed in the preceding section
simultaneously. In order to do this, three problems remain to be solved.
The first, derivation of a black and white film of appropriate Drnin d
Dmax, is expected before, or very early in Phase III. The discus ion in"' '
this technical proposal will therefore be limited to the other problems, c
i. e. very rapid fixing without loss of resolution and without damage to
flexible film substrates, control of contrast, and the combination? of all
the desired. properties in one photosensitive film.
A. , Film Fixing. The materials developed to date are not suitable
for rapid fixinj As shown previously, temperatures necessary for one
minute fixing grade resolution and produce distortion in these materials.
The materials can be modified in several ways in order to obviate the
problem. Materials which avoid the necessity for fixing present the most
promising approach. In this method, photosensitive :agent-dye
combinations are used which are sensitive only to ultraviolet light, and
not to wavelengths found in common sources of illumination.
Another approach is to, modify the fixing technique by using
vacuum, forced hot air, pulse heating, infrared hepg, or similar means.
A third approach is to build into the film a chemical`'ystom that reacts
with the photosensitive agent and deactivates it upon exposure to infrared,
heat or some. 9ther post-exposure treatment. Finally, the use of
thermosetting resins, thermally stable films such as polyphenyleneoxide,
and very thin films may reduce the undesirable effects of heat fixing to the
required degree.
'A-simultaneous attack on each of these approaches to the
solution of theJixing. problem is proposed. Each will account for
.approximately '0-20% of the total effort. The approaches which have been
mentioned above are:
1. films sensitive to ultraviolet light only;
2. modification of present heat fixing technique by use of
auxiliary techniques: vacuum, forced draft, etc.;
3. modification of materials so as to reduce undesirable
effects of heat fixing.
Each of these approaches will be discussed below.
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1. Films insensitive to white light. The primary effort
thus far has been on films which are sensitive to white light. In order to
avoid fixing problems, films sensitive only to ultraviolet would be useful.
Two approaches will be taken. In the first, photosensitive agents will be
sought which are transparent to visible light and which have sufficiently
high bond strength so that visible light will not affect them. The basis for
the suggestion of this approach lies in the observation that some dye-
iodoform mixtures will bleach upon exposure to light absorbed by the dye,
and others bleach only with light absorbed by the iodoform. If the
iodoform is replaced by a photosensitive agent which absorbs only below
about 3000-3400 A?, and if dyes of the latter type, that is, dyes which do
not transfer energy, are used, the films should not be affected by light
from tungsten or fluorescent lamps. The major effort to date. has been
on dyes which transfer energy as they can utilize a higher proportion of
the incident light than can the others, and thus appear considerably more
sensitive to the tungsten sources routinely used for exposure. To utilize
these materials effectively, an efficient mercury source will be built and
compared with a xenon flash unit for effectiveness.
The most likely photosensitive agents are compounds
containing several chlorine atoms. Of these, intriguing possibilities are
polyvinylidene chloride and polyvinyl chloride. These -compounds are
polymers and can act as the film material as well as the photosensitive
agent. Halogenated polymers are known to undergo chain decompositions.
When the elements of HCl are removed from polyvinyl chloride or
polyvinylidene chloride a double bond is formed in the polymer. A
chlorine atom is situated on the chain on a carbon atom adjacent to one
of those in the double bond. Chlorine atoms in such structures are about
--one--hundred times as susceptible to removal as those in other sites. 1
As a result, a chain reaction is possible, increasing the sensitivity of the
system.
On the basis of this reasoning, films of Indophenol Blue
in polyvinyl chloride (PVC) and in polyvinylidene chloride (PVDC) have
been prepared and exposed to tungsten and to mercury sources. The PVC
film showed no bleaching in a 500 watt projector for ten minutes, and the
PVDC film only slight bleaching under the same conditions. Both films
bleached under the mercury source, the PVDC film being considerably
more sensitive.
1. Boyer, R. F., J. Phys. & Colloid Chem., 51., 80 (1947)
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The conditions for exposure and the sensitivity of dyes
in these films will be determined. Similar work will be done with other
commercially available materials such as chlorinated paraffins and
rubbers which contain up to 70% chlorine and which may be more reactive
for structural reasons. Polyvinylbromide2 has been prepared and is
expected to be more photosensitive than the chlorine polymers. However,
it may prove sensitive to white light.
A second approach is to develop the azide process -
discovered in the spring of 1966. In this process, inorganic azides are
illumihated with ultraviolet light and produce a base which then. reacts
with appropriate dyes, bleaching them. This is entirely analogous to the
-bleaching by acid which occurs with some dyes in the halide process.
The main advantages of the azide process are that:
a. The bleached form of the one dye with which this
process has been tried was more colorless (had a lower and more
uniform Dmin) than any film yet produced by the usual process.
b. . A large number of dyes previously ignored because
of insolubility can be examined, because the azides used are water
soluble, and none of the other photosensitive agents are.
c. The azides are completely inert to light above about
3000 A?.
The disadvantages are:
a. Considerable effort will be needed to find compatible
and photographically useful polymer systems .for these materials..
b. They may prove to be photographically slow.
c. A mercury light source would be needed, with. its
attendant inconvenience, 'or perhaps a powerful xenon flash unit.
2. Modification of heat fixing techniques. If the rate
determining step for heat fixing is the diffusion of photosensitive agent
through the polymer matrix to the surface, there is probably not much
that can be done to improve the speed and effectiveness of heat fixing.
If, however, heat fixing is a deactivation by reaction with oxygen or with
2. Alina Ulinska, Zbigniew Mankowski (M. Kopernik Univ., Torun, Poland)
Studia Soc. Sci. Torun. Sect. B2(2), 16 pp. (1960)-Chem. Abstr. 45,
5270d
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polymer or if a reaction of some sort (a "fixing reaction") can be initiated
by heat but. not by ultraviolet and/or visible light, then heat fixing can be
made rapid and effective simultaneously by environmental manipulation.
A search for a fixing reaction is a large undertaking, and will not be
attempted except as a peripheral activity. it -does seem worthwhile,
however, to attempt to improve the efficiency of heat locking by means of
forced warm air and by investigating the effect of oxygen and of selected
additives on heat locking.
3. Modification of materials. High temperature heat fixing
affects dimensional stability and resolution. Polymers exist which show
much greater dimensional stability to high temperatures than those which
have been investigated. One such polymer is polyphenylene oxide, PPO,
recently developed in this laboratory. These polymers will be investigated
both as a medium for carrying the dye-PSA combination, and as a flexible
substrate to be coated. Coatings must be made as thin as feasible, since
fixing time at a given temperature is expected to vary exponentially with
film thickness. Thus, high temperature polymers which are also good
solvents for the dye-PSA systems are needed.
If such high temperature polymers prove effective as
substrates but not as solvents, thermosetting polymers may be used as
solvents. These materials cross-link on heating, and thus reduce
diffusion. Since the dye molecules are much larger than PSA molecules,
dye diffusion' will be affected to a greater extent than that needed for fixing.
This effect may be sufficient to maintain the needed resolution during high
temperature fixing.
B. Contrast Control. Recent experiments have indicated that
the sensitivity of photobleach films is markedly increased when they are
illuminated while warm. In one experiment the sensitivity was increased
by ten times for a temperature rise of about 40 degrees above ambient.
These results point to a method for controlling contrast. The data are
not yet sufficiently quantitative for an accurate estimate of the control
available.
Theoretical considerations indicate, and some experiments
performed seem to bear this out, that all photobleach materials will have
similar H&D curves (Density D versus log Exposure E), differing only
with respect to displacement along the log E axis. A single material, at
different temperatures, should also have similarly displaced parallel
H&D curves. As temperature is raised, the curve is displaced to lower
log E values. If, however, temperature is changed during exposure, the
shape of the curve will be changed, and hence the slope (or gamma) will
be changed also. If the material is hated during exposure, thus
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increasing sensitivity, the slope will increase and conversely, cooling
during exposure will decrease the slope. The measured slopes of
photobleach materials are 0. 9 to 1. 0, with sign opposite to that of silver
halide materials. This means that heating during exposure will be the
preferred mode, and fortunately, is experimentally easier than controlled
cooling. In this regard, experiments have been carried out in this
laboratory on the rapid heating of flexible films by infrared radiation.
Temperatures of 40 to 50 degrees above ambient have been achieved in
such films in less than one second with moderate infrared sources.
These experiments indicate that the necessary rapid, uniform and
controlled heating of the films will not present undue experimental
difficulties.
The objective of contrast control is ttb ;render visible
distinctions between images with small optical density differences.
Another way of achieving this using photobleach materials is to overe*p6se,
when thesired detail is in areas of high optical density, and underexpose
in areas Mf tow optical density. For example, a rough calculation indicates
that areas `of.the original of optical density 1. 70 and 1. 71 can be rendered
in the photobleach copy as 1.00 and 1. 025 by an overexposure of 25 times.
This renders a 0. 6% difference of density into a 2. 5% difference. Although
any portions; of the original with a density below 1. 2 to 1. 4 will be washed
out, the contrast on the shadow area will be increased by a factor of four.
We propose to allot 30% of the effort. `of this program in
Phase III to contrast control, the major portion ofthis time to the technique
of varying gamma by varying the temperature, and a minor effort to
ascertaining the parameters for over or underexposure. Heating techniques
to be ' i9vestigated will include two or more of: infrared, conductive
heatin induction heating or radio frequency heating.
C. Final Film Formulation. The end product of Phase III should
be a film which simultaneously meets or comes close to meeting all nine
of the requirements listed at the beginning of this proposal. It is apparent
that changes made to improve one characteristic may affect the
accomplishments made on another property, either favorably or adversely.
T4 e detailed design of the final film will depend on the technique adopted
for W& scr,.t*tn of the fixing problem. For this reason, the major effort
in the first half of the progt'am year will be spent on the three approaches
to fixing. When a decision has been made on the'i?oach to be used,
work will proceed on the choice of materials to opt ? ize the properties
of the over-all film. It is expected that the design: 6f the film will be
sufficiently definitive at the mid-point`, df Phase III for initiation of the
design of the apparatus to be used with these materials.
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 Th~??al film will be available at user's hoice, on
fle'~v~~r28R51g 'pC7P71~r~r ar w 17 also be
available. However, since paper materials have a low priority in this
program, they may not be as satisfactory as the transparent materials.
D. Summary of Technical Proposal. The work to be done is to
be apportioned as follows:
1. Fixing - approximately 45%
a. system insensitive to white light
b. heat fixing techniques
c. - high temperature materials
2. - Contrast Control - approximately 30%
a. gamma control
b. - exposure control
3. Film Optimization - 25%
a. continuing improvements in dye and photosensitive
agent combinations
b. improvements in substrate: polymer. formulation,
tape and glass coating techniques, papers
c. maximizing of over-all film performance
This program is designed to achieve essentially all of the
objectives listed on page 3 in a single, practical film. It is expected that
this will be achieved by the end of the program proposed herein.
E. Reports. It is assumed that Phase III will constitute a one
year study. Monthly letter reports and a final summary will be submitted.
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